CVE-2026-48818
In versions 1.0.1 and earlier, StaticFiles on Windows is vulnerable to SSRF.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (0.37%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
Starlette is a lightweight ASGI framework/toolkit. In versions 1.0.1 and earlier, StaticFiles on Windows is vulnerable to SSRF. An UNC path such as \\attacker.com\share can cause os.path.realpath to initiate an outbound SMB connection before the path is rejected, exposing the service account’s NTLMv2 credentials for offline cracking or relay even though the HTTP response is only a 404. The issue affects default follow_symlink=False deployments, including frameworks built on Starlette such as FastAPI; POSIX systems and follow_symlink=True are unaffected. The issue is fixed in 1.1.0.
- CVSS 3.1
- 7.5 HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
- EPSS
- 0.37% probability · 30th percentile
- CISA KEV
- Not listed
- Weakness
- CWE-918
- Affected
- encode/starlette
- Source
- security-advisories@github.com
References
- https://github.com/Kludex/starlette/commit/fd53168a7767b6b55ba5af787fd88f49e33cabc5Patch
- https://github.com/Kludex/starlette/pull/3287Patch
- https://github.com/Kludex/starlette/releases/tag/1.1.0Release Notes
- https://github.com/Kludex/starlette/security/advisories/GHSA-wqp7-x3pw-xc5rMitigation, Vendor Advisory
- https://github.com/pypa/advisory-database/tree/main/vulns/starlette/PYSEC-2026-2281.yaml
- https://access.redhat.com/errata/RHSA-2026:30087
- https://access.redhat.com/errata/RHSA-2026:30088
- https://access.redhat.com/errata/RHSA-2026:30089
- https://access.redhat.com/security/cve/CVE-2026-48818
- https://bugzilla.redhat.com/show_bug.cgi?id=2490020
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-48818.json
Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.